(1) Field of the Invention:
The present invention relates to cooling the internal walls, and particularly the refractory lining, of shaft furnaces. More specifically, this invention is directed to cooling boxes intended for installation in the wall of a blast furnace. Accordingly, the general objects of the present invention are to provide novel and improved methods and apparatus of such character.
(2) Description of the Prior Art:
It is well known to provide the walls of blast furnaces with coolers through which cooling water is circulated in the interest of reducing the temperature of the furnace wall to thereby prolong its life. The typical shaft furnace wall has an outer steel shell and an inner lining of refractory material. The coolers are inserted through openings in the shell and into cavities formed in the refractory. In a modern furnace a great number of cooling box-type coolers will be fitted into the side wall of the furnace and will serve not only to cool the furnace but also to secure and support the refractory brickwork which defines the furnace lining. The cooling boxes are typically fabricated from copper or steel or may, in some cases, be comprised partly of copper and partly of steel. The typical prior art cooling box has a shape which is substantially that of a more or less flattened parallelopiped.
It is common for a cooling box to be provided with two cooling circuits; i.e., two separate flow paths through which cooling water may be circulated. Thus, in one type of prior art cooling box a first primary cooling circuit will extend along the external side walls of the cooling box into the "nose" portion thereof and a second cooling circuit will form a loop which is located in the cooling box to the inside of the first cooling circuit. The two cooling circuits are preferably separately fed with coolant whereby the second circuit may be kept in operation in the event of damage to the primary circuit. Damage to the externally positioned primary cooling circuit may result from wear of the "nose" portion of the cooling box; the "nose" portion of the cooling box being the most inwardly disposed part of the device and thus subject to the harshest operating conditions.
In actual practice, continuing to discuss prior art cooling boxes of the type having separately fed external primary and internal secondary cooling circuits, damage to the external primary cooling circuit requires that it be put out of operation. Termination of delivery of coolant to the external primary cooling circuit results in discontinuing the direct cooling of the peripheral portions of the cooling box and particularly of the side walls of the box. Accordingly, the erosion or other wear which resulted in the necessity of terminating operation of the external cooling circuit will continue at an increasing rate and will jeopardize the integrity of the internal or secondary cooling circuit. In this regard it is to be noted that the internal cooling circuit is generally designed to be less resistant to failure than the external circuit. Accordingly, at best, the provision of a pair of separate coolant flow loops in a conventional cooling box merely affords the furnace operator a short margin of time in which to replace a cooling box having a nose portion which has suffered wear.
It has been proposed to obviate the above discussed problem by providing a cooling box having a first or primary cooling circuit in the form of a loop which extends into the interior of the nose portion of the cooling box and which has two branches, functioning as the coolant supply and discharge conduits, arranged relatively close together and at the center of the cooling box at the end thereof which is adjacent the furnace-shell. The entire first cooling loop is immersed in a "second cooling circuit"; i.e., the interior of the cooling box is a cavity which functions as the "second cooling circuit". The coolant in the "second cooling circuit" is in contact with all of the walls of the cooling box with the exception of the nose portion thereof. In theory, upon failure of the first cooling circuit, the "second cooling circuit" would insure adequate cooling of the side walls of the cooling box after the cooling of the damaged nose portion of the box was discontinued. In actual practice, however, this desired effect does not result because the coolant will not circulate satisfactorily through the "second cooling circuit". There may, in fact, be stagnation regions or uncontrollable eddys in which the coolant does not circuiate at all. This results in the lateral surfaces, and even the upper and lower surfaces, of the cooling box not being properly cooled and this problem is aggravated after the first cooling circuit or loop has been put out of operation. Accordingly, cooling boxes which define a "second cooling circuit" in which a portion of the first cooling circuit is immersed have suffered from the same disadvantages as prior art cooling boxes including separately fed coolant flow paths which define primary external and secondary internal cooling circuits.